diff --git a/archive-zip.c b/archive-zip.c
index 28e7352e98..ae5572ae20 100644
--- a/archive-zip.c
+++ b/archive-zip.c
@@ -160,7 +160,7 @@ static int write_zip_entry(const unsigned char *sha1,
 	void *buffer = NULL;
 	void *deflated = NULL;
 
-	crc = crc32(0, Z_NULL, 0);
+	crc = crc32(0, NULL, 0);
 
 	path = construct_path(base, baselen, filename, S_ISDIR(mode), &pathlen);
 	if (verbose)